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kdb: Don't back trace on a cpu that didn't round up

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If you have a CPU that fails to round up and then run 'btc' you'll end
up crashing in kdb becaue we dereferenced NULL.  Let's add a check.
It's wise to also set the task to NULL when leaving the debugger so
that if we fail to round up on a later entry into the debugger we
won't backtrace a stale task.

Signed-off-by: Douglas Anderson <dianders@chromium.org>
Acked-by: Daniel Thompson <daniel.thompson@linaro.org>
Signed-off-by: Daniel Thompson <daniel.thompson@linaro.org>
This commit is contained in:
Douglas Anderson 2018-12-04 19:38:28 -08:00 committed by Daniel Thompson
parent 87b0959285
commit 162bc7f5af
3 changed files with 14 additions and 8 deletions
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4
kernel/debug/debug_core.c
View File

@ -592,6 +592,8 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
arch_kgdb_ops.correct_hw_break();
if (trace_on)
tracing_on();
kgdb_info[cpu].debuggerinfo = NULL;
kgdb_info[cpu].task = NULL;
kgdb_info[cpu].exception_state &=
~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
kgdb_info[cpu].enter_kgdb--;
@ -724,6 +726,8 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs,
if (trace_on)
tracing_on();
kgdb_info[cpu].debuggerinfo = NULL;
kgdb_info[cpu].task = NULL;
kgdb_info[cpu].exception_state &=
~(DCPU_WANT_MASTER | DCPU_IS_SLAVE);
kgdb_info[cpu].enter_kgdb--;

11
kernel/debug/kdb/kdb_bt.c
View File

@ -186,7 +186,16 @@ kdb_bt(int argc, const char **argv)
kdb_printf("btc: cpu status: ");
kdb_parse("cpu\n");
for_each_online_cpu(cpu) {
sprintf(buf, "btt 0x%px\n", KDB_TSK(cpu));
void *kdb_tsk = KDB_TSK(cpu);
/* If a CPU failed to round up we could be here */
if (!kdb_tsk) {
kdb_printf("WARNING: no task for cpu %ld\n",
cpu);
continue;
}
sprintf(buf, "btt 0x%px\n", kdb_tsk);
kdb_parse(buf);
touch_nmi_watchdog();
}

7
kernel/debug/kdb/kdb_debugger.c
View File

@ -118,13 +118,6 @@ int kdb_stub(struct kgdb_state *ks)
kdb_bp_remove();
KDB_STATE_CLEAR(DOING_SS);
KDB_STATE_SET(PAGER);
/* zero out any offline cpu data */
for_each_present_cpu(i) {
if (!cpu_online(i)) {
kgdb_info[i].debuggerinfo = NULL;
kgdb_info[i].task = NULL;
}
}
if (ks->err_code == DIE_OOPS || reason == KDB_REASON_OOPS) {
ks->pass_exception = 1;
KDB_FLAG_SET(CATASTROPHIC);